<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Document</title>
  </head>
  <body>
    <script>
      var a = 10;
      var b = ++a + 2;		// b = 11 + 2，a = 11
      var c = b++ + 2;		// c = 13 + 2，b = 14
      var d = c++ + ++a;	// d = 15 + 12，c = 16，a = 12
    </script>
  </body>
</html>